Impedance and thus electrical loss increase in proportion to distance between a battery and a load supported by the battery. In applications where main system loads are at a greater distance from the battery than desirable due to physical layout and placement, the source impedance may be too high to supply adequate power during heavy loads, leading to a high risk of system brownout.
To provide increased battery placement flexibility, some systems include significant bulk capacitors near loads that exhibit high load transients, effectively decreasing high transient current draw from the battery by supplying a lower impedance source and thereby reducing the voltage drop associated with the higher impedance of the battery source. However, bulk capacitors consume already-limited circuit board surface area and add to system manufacturing costs. Additionally, depending on the load profile, achieving a target energy storage and impedance profile may limit peak loading below target levels if reliant on bulk capacitors. Other systems increase battery placement options and run-time capacity by including multiple batteries. If batteries have identical charge characteristics (e.g., total capacity and relative charge state at any given point in time), the batteries may be connected in series (to increase voltage level) or in parallel (to keep same the voltage level but increase total capacity) and permitted to charge and discharge at substantially identical rates. If, however, selected batteries have disparate charge and discharge characteristics, battery life preservation may depend on regular operation of the batteries at different charge and/or discharge rates, leading to a number of design challenges.